Boston Celtics rookie Jared Sullinger will be the first to admit that his transition to the NBA has been uneven. Through 27 games, he is averaging 5.1 points and 5.1 rebounds on 47.9 percent shooting, acceptable enough numbers for the No. 21 pick in last year’s draft. But Sullinger has struggled with consistency, and because he lacks standout size or athleticism, he has been susceptible to having his shot blocked on the offensive end and general abuse on the defensive end.

That’s why Sullinger, who briefly held a spot in Boston’s starting five early in the year, has had some stretches in which he’s played 30 minutes, and some in which he has not broken the 10-minute mark. But the Celtics are hoping that his Christmas Day performance—he scored 16 points on 6-for-7 shooting against the undersize Nets—will be a harbinger of good things.

That led to what has now become one of coach Doc Rivers’ best backhanded compliments: “Jared was wonderful. He’s such a smart player. When you watch him, you don’t see rookie. You just see a big fat guy playing basketball.”

Indeed, Sullinger's conditioning and ability to keep up with the overall speed of the game have been concerns. He has a knack for rebounding, but he has not been able to adjust to the bigger players he sees at this level. “It is just consistency,” Sullinger said. “It is trying to be able to go out and find a way to contribute every night. In college, I knew I was going to get the ball and impact the game. Here, it is just finding a way to help your team win.”

Last year, as a sophomore at Ohio State, Sullinger averaged 17.5 points and 9.2 rebounds. He was considered a lottery pick for much of the year, but scouts began wavering on that late in the season and when he was given a medical red flag because of back issue, his stock plummeted. That’s how the Celtics were able to draft him so late.

Now, though, the Celtics need him to be productive. Boston is very thin up front, outside of Kevin Garnett, and the Celtics have experimented with Brandon Bass, Sullinger and now Jason Collins in the starting five. They briefly signed center Darko Milicic, lost Chris Wilcox for a few weeks with a thumb injury and signed the D-League’s leading shot-blocker, Jarvis Varnado. But the Celtics have been looking to add a veteran big man via trade—but if Sullinger can pick up his play, that might not be necessary.

“He’s learning still that there’s a different pace that you have to play in this league compared to Ohio State, and we’re on him about it and he’s improving,” Rivers said. “He’s a smart, smart kid on the floor.”